HARDNESS, MICROSTRUCTURE AND SURFACE CHARACTERIZATION OF LASER GAS NITRIDED COMMERCIALLY PURE TITANIUM USING HIGH-POWER CO2-LASER

Surface nitriding of commercially pure (CP) titanium was carried out u sing high power CO2 laser at pure nitrogen and dilute nitrogen (N-2 Ar) environment. The hardness, microstructure. and melt pool configura tion of the laser melted titanium in helium and argon atmosphere was c ompared with laser melting at pure and dilute nitrogen environment. Th e hardness of the nitrided layer was of the order of 1000 to 1600 HV, The hardness of the laser melted titanium in the argon and helium atmo sphere was 500 to 1000 HV, Using x-ray analysis the formation of TiN a nd Ti2N phase was identified in the laser nitrided titanium. The prese nce of nitrogen in the nitrided zone was confirmed using secondary ion mass spectroscopy (SIMS) analysis. The microstructures revealed dense ly populated dendrites in the sample nitrided at 100 % N-2 environment and thinly populated dendrites in dilute environment. The crack inten sity was large in the nitrided sample at pure nitrogen, anti few crack s were observed in the 50 % N-2 + 50 % Ar environment.